1. Field of the Invention
The present invention generally relates to an inductor structure, and more particularly, to an inductor structure capable of improving Q-factor (quality factor).
2. Description of Related Art
In general speaking, as an inductor acquires energy storing and releasing functions through electromagnetic conversion, the inductor can be used as an element for stabilizing current. An inductor is broadly applicable in many fields, such as in radio frequency circuit (RF circuit), voltage-controlled oscillator (VCO), low noise amplifier (LNA) or power amplifier (PA). In an integrated circuit (IC), an inductor plays a very important and extreme challenging role and serves as a passive component. In terms of the efficiency thereof, an inductor with higher quality means the inductor has a higher quality factor represented by Q-factor, which is defined by:Q=ω×L/R where ω is angular frequency, L is inductance of the inductor coil and R is resistance considering inductance loss under specific frequencies.
There are various methods and techniques today available for incorporating an inductor with IC process. However, in an IC, the limitation of the metal thickness of an inductor and the interference on an inductor by a silicon substrate would degrade the quality of the inductor. To overcome the problem in the prior art, the conductor loss is reduced by increasing the metal thickness of an inductor or the wire width of the inductor coil so as to advance the Q-factor of inductor. When the above-mentioned conventional scheme is used in a symmetric differential inductor, in particular, along with increasing the wire width of the inductor coil, a coupling in certain extents between the two coils of the inductor and the substrate occurs, which affects the efficiency of the inductor.
In short, how to solve the various problems encountered in the above-mentioned process, advance Q-factor of an inductor and reduce conductor loss has become an important project for the manufactures to develop.